Recent changes to transmission line design
standards and the impact on new construction and
ageing assets in the Pilbara
E...
What will we cover in this presentation?
1. Introduction
2. The Pilbara, where are we?
3. AS/NZS 7000:2010 key differences...
The Pilbara, where are we?
• Region D with cyclonic wind speeds
• Return periods for transmission lines generally 200+ yea...
AS/NZS 7000:2010 key differences amongst others
Wind load
• No need to apply 10% amplification to the wind speeds in
AS/NZ...
AS/NZS 7000:2010 key differences amongst others
Wind load
AS/NZS 7000:2010 key differences amongst others
Insulator swing
• High wind in insulator swing calculations has been typic...
AS/ NZS 7000:2010 key differences amongst others
Insulator swing
• Low wind and moderate wind is 100 Pa and 300 Pa
• Some ...
AS/ NZS 7000:2010 key differences amongst others
Insulator swing
• Blowout calculation is linked to the serviceability win...
AS/ NZS 7000:2010 key differences amongst others
Insulator swing
AS/ NZS 7000:2010 key differences amongst others
Insulator swing … suggested approach…
• The wind speed derived should be ...
AS/NZS 7000:2010 key differences amongst others
Conductor assessment (strength and serviceability limits)
• The below tabl...
AS/NZS 7000:2010 key differences amongst others
Comparison of Cb1 and AS7000 (for conductors in the Pilbara region)
Wind S...
AS/NZS 7000:2010 key differences amongst others
Pole foundation assessment
• In the past utilities have used C(b)1 suggest...
AS/NZS 7000:2010 key differences amongst others
Pole foundation assessment
• Mindset exists that “We have done this in the...
AS/NZS 7000:2010 key differences amongst others
Pole foundation assessment
AS/NZS 7000:2010 key differences amongst others
Pole foundation assessment
Tower Testing
Tower Testing
• Failures exhibit load sharing
issues in lattice steel
• Important to understand tower
failur...
Aged transmission lines
What do we do in case of failures?
• Gradual ageing of steel structures exposed to extreme
weather...
Aged transmission lines
What do we do in case of failures?
• There is a need to consider design of transmission lines
with...
Aged transmission lines
What do we do in case of failures?
• Wednesday 28th September TransGrid had a failure on
the 220kV...
Aged transmission lines
What do we do in case of failures?
• Tower 558 has failed in the “classical” manner of
compression...
Aged transmission lines
TransGrid Failure Event
28/09/2011 220kV Line
from Darlington Point to
Buronga, NSW
• Region A7 Do...
Aged transmission lines
TransGrid Failure Event
28/09/2011 220kV Line
from Darlington Point to
Buronga
Aged transmission lines
TransGrid Failure Event
28/09/2011 220kV Line
from Darlington Point to
Buronga
Aged transmission lines
Leigh Creek to Davenport 132kV line experienced a cyclone
in SA
Helicopter stringing in the Pilbara
Some recent challenges experienced
• Access constraints
• Cultural heritage sites
• Ri...
Helicopter stringing in the Pilbara
YM-CL 220kV Stringing Detail
• Helicopter fitted with side
pull rather than belly hook...
Helicopter stringing in the Pilbara
YM-CL 220kV Stringing Detail
• Helicopter pulls the cable
out sideways, to ensure
visi...
Helicopter stringing in the Pilbara
YM-CL 220kV Stringing Detail
• Pulling order planned to
ensure that cables already
str...
Helicopter stringing in the Pilbara
YM-CL 220kV Stringing Detail
• Stringing broken in to 13 pulls
• 7 of the 13 pulls inv...
Helicopter stringing in the Pilbara
Advantages
• Schedule improvement
• 4.5km drawwire pull takes approximately 45 minutes...
Helicopter stringing in the Pilbara
Current industry practice in tower installation
Current industry practice in tower installation
Current industry practice in tower installation
Current industry practice in tower installation
Current industry practice in tower installation
Changing the way we do things? Counter arguments by stakeholders
• Crane r...
Current industry practice in tower installation
• Incidents reported in failures
Current industry practice in tower installation
• Incidents reported in failures
• Close Call for Big Truck Mount
01/17/14...
Current industry practice in tower installation
New method of tower installation
“Safety guide” design
This allows crane operators to lower the top section without manual...
New method of tower installation
New method of tower installation
New method of tower installation
Site Construction Team developed option which included:
• Purpose-made temporary “docking...
New method of tower installation
New method of tower installation
New method of tower installation
New method of tower installation
New method of tower installation
Achievement of outcomes
• Eliminated the need for riggers to work under suspended loads o...
New method of tower installation
Longer splice plates significantly improves landing of the superstructure
Recognitions/Awards
Recognition in the Australian Industry to promote safety and innovation
in current practices for Tower...
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Jacobs Recent changes to transmission line design standards and the impact on new construction and ageing assets in the Pilbara

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Jacobs Recent changes to transmission line design standards and the impact on new construction and ageing assets in the Pilbara

  1. 1. Recent changes to transmission line design standards and the impact on new construction and ageing assets in the Pilbara ENGINEERS AUSTRALIA ASIF BHANGOR, PRINCIPAL ENGINEER AARON HAMILTON, SENIOR ELECTRICAL ENGINEER
  2. 2. What will we cover in this presentation? 1. Introduction 2. The Pilbara, where are we? 3. AS/NZS 7000:2010 key differences amongst others 4. Tower testing 5. Aged transmission lines, what do we do in case of failures? 6. Helicopter stringing 7. Current industry practice in tower installation 8. New method of tower installation 9. Recognitions/Awards
  3. 3. The Pilbara, where are we? • Region D with cyclonic wind speeds • Return periods for transmission lines generally 200+ years whilst distribution lines typically 50/100 years • Regional wind speed for say 200 years return is 72m/s • Indigenous heritage sites, priority ecological areas & rivers • Access constraints • Crossing 3rd party infrastructure sensitive to shutdowns – Mining company railways – Mining or Industry distribution and transmission lines – Highways
  4. 4. AS/NZS 7000:2010 key differences amongst others Wind load • No need to apply 10% amplification to the wind speeds in AS/NZS 7000:2010 • No need to apply downdraft (high intensity winds) for regions C and D
  5. 5. AS/NZS 7000:2010 key differences amongst others Wind load
  6. 6. AS/NZS 7000:2010 key differences amongst others Insulator swing • High wind in insulator swing calculations has been typically mentioned as 500 Pa for power frequency clearance of 500mm
  7. 7. AS/ NZS 7000:2010 key differences amongst others Insulator swing • Low wind and moderate wind is 100 Pa and 300 Pa • Some utilities have used 240 Pa as moderate wind
  8. 8. AS/ NZS 7000:2010 key differences amongst others Insulator swing • Blowout calculation is linked to the serviceability wind but insulator swing talks about high wind (limiting to 500 Pa only) • If we apply maximum wind of the Pilbara, we get large swing angles which lead to bracket extensions for clearances
  9. 9. AS/ NZS 7000:2010 key differences amongst others Insulator swing
  10. 10. AS/ NZS 7000:2010 key differences amongst others Insulator swing … suggested approach… • The wind speed derived should be adjusted for the terrain, height multipliers from AS1170.2 and considering a drag factor of 1.2 • In addition, the wind speed is reduced for the effect of span reduction factors which takes into account the spatial characteristics of wind gusts and inertia offered by the conductors. See figure B5 in AS1170.2 Page 129 • For easement calculations, refer to item R4 in AS7000 and Cb1 2006 table 10.3 for the 5 – 10 minutes averaging period conversion which converts it to a serviceability wind for checking the easement
  11. 11. AS/NZS 7000:2010 key differences amongst others Conductor assessment (strength and serviceability limits) • The below table highlights the factored approach in conductor assessment
  12. 12. AS/NZS 7000:2010 key differences amongst others Comparison of Cb1 and AS7000 (for conductors in the Pilbara region) Wind Speeds up to 90m/sec for conductor selection (including height multipliers) Conductor type UTS (kN) Ft, MWT (kN) Ruling span (m) Special Diving ACSR (30/6/3.5+1/3.65) 146.0 119.4 470.0 AAAC Sapphire (37/3.75) 115.0 81.1 341.0 AACSR/AC/1120 (42/19/3.25) 264.5 145.0 360.0 Criteria/ Cb1 Conductor type 0.7UTS 1.5Ft Special Diving ACSR (30/6/3.5+1/3.65) 102.2 179.0 Conductor fails AAAC Sapphire (37/3.75) 80.5 121.6 Conductor fails AACSR/AC/1120 (42/19/3.25) 185.2 217.5 Conductor fails Criteria/(Failure/ Strength) AS7000 Conductor type 0.9UTS 1.25Ft Special Diving ACSR (30/6/3.5+1/3.65) 131.4 149.2 Conductor fails AAAC Sapphire (37/3.75) 103.5 101.3 OK AACSR/AC/1120 (42/19/3.25) 238.1 181.3 OK Criteria/(Damage/ Serviceability) Non Linear AS7000 Conductor type 0.7UTS 1.00Ft Special Diving ACSR (30/6/3.5+1/3.65) 102.2 119.4 Conductor fails AAAC Sapphire (37/3.75) 80.5 81.1 Conductor fails AACSR/AC/1120 (42/19/3.25) 185.2 145.0 OK Criteria/ (Damage/ Serviceability) Linear AS7000 Conductor type 0.5UTS 1.00Ft Special Diving ACSR (30/6/3.5+1/3.65) 73.0 119.4 Conductor fails AAAC Sapphire (37/3.75) 57.5 81.1 Conductor fails AACSR/AC/1120 (42/19/3.25) 132.3 145.0 Conductor fails Conductor assessment
  13. 13. AS/NZS 7000:2010 key differences amongst others Pole foundation assessment • In the past utilities have used C(b)1 suggested empirical assessment of L/10+0.6 for foundation depths – having no interaction with soil data • Historically, utilities have deemed this acceptable for wood poles in region A where wind speeds are around 39 – 43m/s • However, in the Pilbara where cyclonic wind speeds are present due care has to be considered for poles carrying mine load thus requiring higher reliability (basically no foundation failures acceptable)
  14. 14. AS/NZS 7000:2010 key differences amongst others Pole foundation assessment • Mindset exists that “We have done this in the past using L/10+0.6m so why increase the embedment depth now?” • More recently, utilities have moved away from L/10+0.6m embedment with proper soil interaction methods such as Broms, Brinch & Hansen etc. • Essential Energy, Electranet, Powerlink, Energy Australia design standards all refer to Brinch & Hansen now • Please refer to Table 9.7 of handbook HB331 which states disadvantages of the L/10+0.6(0.8) formula
  15. 15. AS/NZS 7000:2010 key differences amongst others Pole foundation assessment
  16. 16. AS/NZS 7000:2010 key differences amongst others Pole foundation assessment
  17. 17. Tower Testing Tower Testing • Failures exhibit load sharing issues in lattice steel • Important to understand tower failures are catastrophic in nature • Hence the need to test towers and eliminate any issues in load sharing between members, plates, bolts etc. • Leg loads for cyclonic wind regions reach to around 2000kN per leg
  18. 18. Aged transmission lines What do we do in case of failures? • Gradual ageing of steel structures exposed to extreme weather events exposes owners to high cost of refurbishment, let alone lost time of production if local generation does not exist • Generally utilities have dealt with this problem using emergency response structures (i.e. Lindsey Guyed Masts) • The network in the Pilbara is at risk…failures mean complete shutdown…
  19. 19. Aged transmission lines What do we do in case of failures? • There is a need to consider design of transmission lines with higher reliability (i.e. 500 years return wind speeds) and a high degree of accuracy when it comes to detailing and fabrication of steel for new projects • For ageing projects, there is a need to frequently check and maintain/ replace the ageing towers, conductors, and insulators using effective maintenance plans
  20. 20. Aged transmission lines What do we do in case of failures? • Wednesday 28th September TransGrid had a failure on the 220kV line from Darlington Point to Buronga • The failure was at tower 557 and 558, approximately 30 kms east of Balranald (“in the middle of nowhere” was the first description). The cause was a high wind event • 3 towers have been damaged. Initially, towers 557 and 558 failed on the Wednesday night • On the morning of Friday 30th September, leg buckling on Tower 556 was observed • The line has been restored using timber pole emergency structures – 4 structures have been used
  21. 21. Aged transmission lines What do we do in case of failures? • Tower 558 has failed in the “classical” manner of compression failure in the legs and has fallen at 90 deg to the line direction • The foundation shows obvious signs of severe corrosion of the reinforcement and necking of the remaining reo at failure • Some analysis needed to check the reo and concrete to determine the cause and age of the corrosion (an old construction joint? locally aggressive soil?)
  22. 22. Aged transmission lines TransGrid Failure Event 28/09/2011 220kV Line from Darlington Point to Buronga, NSW • Region A7 Downdraft winds (high intensity winds) • Zone II, Span reduction factor = 1.0 (0-200m spans) • Wind speeds up to 43m/s (1.1kPA)
  23. 23. Aged transmission lines TransGrid Failure Event 28/09/2011 220kV Line from Darlington Point to Buronga
  24. 24. Aged transmission lines TransGrid Failure Event 28/09/2011 220kV Line from Darlington Point to Buronga
  25. 25. Aged transmission lines Leigh Creek to Davenport 132kV line experienced a cyclone in SA
  26. 26. Helicopter stringing in the Pilbara Some recent challenges experienced • Access constraints • Cultural heritage sites • River crossings • Priority ecological areas • Crossing 3rd party infrastructure sensitive to shutdowns • Mining company railways • Mining or Industry distribution and transmission lines • Highways
  27. 27. Helicopter stringing in the Pilbara YM-CL 220kV Stringing Detail • Helicopter fitted with side pull rather than belly hook • Side pull is a customised piece of equipment designed specifically for stringing transmission lines • Side pull increases the helicopter fuel efficiency over a belly hook • Pilots prefer side pull as complete assembly is visible
  28. 28. Helicopter stringing in the Pilbara YM-CL 220kV Stringing Detail • Helicopter pulls the cable out sideways, to ensure vision can be maintained in the direction of travel and the direction of load
  29. 29. Helicopter stringing in the Pilbara YM-CL 220kV Stringing Detail • Pulling order planned to ensure that cables already strung are in front of or below the height of the aircraft rotor system • At no point should cables be behind the aircraft at the same height as the one being pulled
  30. 30. Helicopter stringing in the Pilbara YM-CL 220kV Stringing Detail • Stringing broken in to 13 pulls • 7 of the 13 pulls involved 5 towers or fewer • Generally helicopter pulled draw wire for phase conductors and Earthwire and OPGW direct • Direct pulls need to be done under tension to keep off ground • Phase conductors are generally not pulled direct due to the weight, distance from the ground • Helicopter used to pull all conductors direct for rail and line crossings (due to outage limitations)
  31. 31. Helicopter stringing in the Pilbara Advantages • Schedule improvement • 4.5km drawwire pull takes approximately 45 minutes • 12km OHEW or OPGW pull under tension takes approximately 3 hours • Critical path moves to linesmen sagging and terminating • Low impact on heritage sites (line crosses directly over 18) • Simplified stringing over heavily vegetated river crossing (620m) • Simplified, faster stringing over existing 132kV transmission lines • Simplified, faster stringing over rail
  32. 32. Helicopter stringing in the Pilbara
  33. 33. Current industry practice in tower installation
  34. 34. Current industry practice in tower installation
  35. 35. Current industry practice in tower installation
  36. 36. Current industry practice in tower installation
  37. 37. Current industry practice in tower installation Changing the way we do things? Counter arguments by stakeholders • Crane rated 10 times higher than load • Load calculations done for all critical lifts • Lift plans reviewed and signed off by engineer • Crane inspected at regular intervals • Crane operator is very experienced and has worked with rigging team for a long time • Rigging equipment rated 5 times higher than load • Rigging equipment inspected daily by crew as well as monthly inspections by accredited third party inspectors. • Rigging crew is well trained and very experienced in tower construction • Verification of competence of all riggers and crane operator • PPE inspected daily including safety harnesses, ropes etc. • Very quick installation reducing riggers time spent on the tower and risk of fall
  38. 38. Current industry practice in tower installation • Incidents reported in failures
  39. 39. Current industry practice in tower installation • Incidents reported in failures • Close Call for Big Truck Mount 01/17/14 • Newcastle, Australia • A 54 meter truck mounted lift lost balance near Newcastle, Australia when the ground gave way under one of its outriggers. • Fortunately the boom came to rest against the pylons of the high tension power line that it was helping to install – no one was injured or hurt in the incident
  40. 40. Current industry practice in tower installation
  41. 41. New method of tower installation “Safety guide” design This allows crane operators to lower the top section without manual intervention of crew • Once the lower portion of the tower is installed on the ground and fitted with the foundation base, it is fitted at the connection point to the top structure with the safety bracket • The top superstructure is suspended by the crane operator and lowered into the safety bracket, landing the top superstructure inside the bracket. The load of the top superstructure is relieved by the crane operator as the weight of the top does not rest on the steel itself • The rigging personnel can then go to the top section and connect the relevant bolts to the holes of the relevant plates and release the safety bracket. This enables them to work without being under suspended load
  42. 42. New method of tower installation
  43. 43. New method of tower installation
  44. 44. New method of tower installation Site Construction Team developed option which included: • Purpose-made temporary “docking brackets” to be installed at the fixing positions to ease “landing” of the suspended structures onto their bases, without the need for riggers to be under the suspended loads. • Installation of temporary brackets to guide sections in to place isn’t new, but their use has to date been limited to helicopter based tower construction. • Spacing the splice plates of the suspended structure sections (mid sections), to gape open, thus easing the landing of those structures through carefully lowering, with control provided by tag lines with the riggers safely away from danger.
  45. 45. New method of tower installation
  46. 46. New method of tower installation
  47. 47. New method of tower installation
  48. 48. New method of tower installation
  49. 49. New method of tower installation Achievement of outcomes • Eliminated the need for riggers to work under suspended loads or manually move the sections into place risking injury. • Riggers are no longer exposed to the swinging momentum of the tower sections. • Does not require additional brackets to be installed or design modifications for the most part and the changes were mostly procedural. Existing splice plates join the adjacent sections, which is easy to implement. • Developed new, safer site construction methodology that involves sections of the tower being landed onto the bottom sections with the combined use of brackets, guide ropes and or other equipment and material already available on site.
  50. 50. New method of tower installation Longer splice plates significantly improves landing of the superstructure
  51. 51. Recognitions/Awards Recognition in the Australian Industry to promote safety and innovation in current practices for Tower Design and Installation

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